It is known to dye keratin fibers, in particular human hair, with dyeing compositions containing oxidative coloring precursors, generally called oxidative bases, such as ortho- or para-phenylenediamines, ortho- or para-aminophenols and heterocyclic compounds. These oxidative bases are generally combined with couplers. These bases and these couplers are colorless or weakly colored compounds which, combined with oxidizing products, can give rise to colored compounds through an oxidative condensation process.
This type of coloring by oxidation makes it possible to obtain colors with very high visibility, coverage of white hair and in a wide variety of shades but it results in damage to the keratin fibers by the use of oxidizing agents (in particular by repeated application or by combination with other hair treatments).
On the other hand, it is also known to dye keratin fibers, in particular human hair, with dyeing compositions containing direct dyes. Conventional direct dyes are in particular the following: benzene nitrates, anthraquinones, nitropyridines, azos, xanthines, acridines, azines, and triarylmethane type or natural colorings.
For example, JP-A-2002-241245 and WO 2009/047916 disclose a composition for dyeing hair, including a direct dye.
Hair coloration using direct dyes has advantages over hair coloration using oxidative dyes: it has no allergic issues, no damage to the hair, and it gives vivid color visibility.